Electronic Components 1-Channel Single ADC Semiflash 1Msps 8-bit Parallel 20-Pin SOIC W AD7821KRZ Integrated Circuits

Electronic Components 1-Channel Single ADC Semiflash 1Msps 8-bit Parallel 20-Pin SOIC W Tube AD7821KRZ Integrated Circuits





Functional Description :

1. Fast Conversion Time

The half-flash conversion technique, coupled with fabrication on Analog Devices’ LC²MOS process, enables a very fast conversion time. The conversion time for the WR-RD mode is 660 ns, with 700 ns for the RD mode.

2. Built-In Track-and-Hold

This allows input signals with slew rates up to 1.6 V/μs to be converted to 8 bits without an external track-and-hold. This corresponds to a 5 V peak-to-peak, 100 kHz sine wave signal.

3. Total Unadjusted Error

The AD7821 features an excellent total unadjusted error figure of less than ±1 LSB over the full operating temperature range.

4. Unipolar/Bipolar Input Ranges

The AD7821 is specified for single-supply (+5 V) operation with a unipolar full-scale range of 0 to +5 V, and for dual-supply (±5 V) operation with a bipolar input range of ±2.5 V. Typical performance characteristics are given for other input ranges.

5. Dynamic Specifications for DSP Users

In addition to the traditional ADC specifications, the AD7821 is specified for ac parameters, including signal-to-noise ratio, distortion, and slew rate.

Features :

• Fast Conversion Time: 660 ns Max
• 100 kHz Track-and-Hold Function
• 1 MHz Sample Rate
• Unipolar and Bipolar Input Ranges
• Ratiometric Reference Inputs
• No External Clock
• Extended Temperature Range Operation
• Skinny 20-Lead DlPs, SOIC, and 20-Terminal Surface-Mount Packages

General Description :

The AD7821 is a high speed, 8-bit, sampling, analog-to-digital converter that offers improved performance over the popular AD7820. It offers a conversion time of 660 ns (versus 1.36 μs for the AD7820) and 100 kHz signal bandwidth (versus 6.4kHz). The sampling instant is better defined and occurs on the falling edge of WR or RD. The provision of a V_SS pin (Pin 19) allows the part to operate from ±5 V supplies and to digitize bipolar input signals. Alternatively, for unipolar inputs, the V_SS pin can be grounded and the AD7821 will operate from a single +5 V supply, like the AD7820.

The AD7821 has a built-in track-and-hold function capable of digitizing full-scale signals up to 100 kHz max. It also uses a half-flash conversion technique that eliminates the need to generate a CLK signal for the ADC.

The AD7821 is designed with standard microprocessor control signals (CS, RD, WR, RDY, INT) and latched, three-state data outputs capable of interfacing to high speed data buses. An overflow output (OFL) is also provided for cascading devices to achieve higher resolution.

The AD7821 is fabricated in Linear Compatible CMOS (LC²MOS), an advanced, mixed technology process combining precision bipolar circuits with low power CMOS logic. The part features a low power dissipation of 50 mW.

Characteristic Chart :

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